This invention relates to ground fault interrupters (GFIs) and more particularly to a GFI provided with an indicator for indicating whether the GFI has been properly installed.
GFIs are devices which detect ground leakage currents of such small magnitudes that normal overload and short circuit breakers or fuses are not responsive thereto, but which could well be lethal currents to human beings. Although the sensitivity of such devices varies, they have typically been designed to open the circuit if the leakage current exceeds 5 milliamps. Their importance in protecting human life is readily apparent when one considers that currents in excess of 60 milliamps are generally lethal and, depending on the physical condition of the person and the electrical path which is created, substantially smaller currents can also be lethal or, at the least, quite painful and dangerous.
It is, therefore, quite important to encourage the installation and use of GFIs in industrial and residential use, especially under specific circumstances where the likelihood of potential hazards is greater or the possibilities of lethal currents are more probable. One such use would be in electrical circuits for home swimming pools.
To encourage their use, it is desirable to provide less expensive GFIs as well as reducing the size of such models for more convenient installation. It is also apparent that, although in many instances GFIs will typically be installed by trained technicians, it is a good possibility that many home owners and amateur electricians will endeavor to reduce their cost and install GFIs themselves.
In GFIs, it is only necessary to provide a circuit breaker in series with the line conductor of the wiring system to safely disconnect the circuit should leakage current occur. However, if the interrupter is improperly installed and the circuit breaker is connected in series with the neutral conductor, rather than the line conductor, then the interrupter will not provide the protection it is designed for. For this reason, circuit breakers are included in series with both the line and neutral conductors in units likely to be installed by the amateur to provide adequate protection even if the lines are reversely connected during installation. In fact, the Underwriters Laboratories has required such dual circuit breakers in GFIs likely to be installed by an amateur. This, however, needlessly increases the cost of the item by necessitating the provision of an additional circuit breaker and also increases the space requirements of the interrupter, inasmuch as a circuit breaker occupies a substantial volume in relation to the other components of a GFI.